The spinal column is comprised of twenty-six interlocking vertebrae. These vertebrae are separated by disks. The spine provides load-bearing support for one-half of the body's mass and it protects the nerves of the spinal column. The disks provide shock absorption and facilitate the bending of the spine.
The combination of the vertebrae and disks at each vertebral segment allows for motion of the spine, in particular, flexing, rotation, and extension. The motion and support functions of the spine, in combination with the many interlocking parts and nerve roots associated with the spinal column can result in back pain due to various reasons. Such back pain may result from the degeneration of disks due to age, disease, or injury. Further, vertebral bodies may be compromised due to disease or defect, such as a tumor, or injury, such as fracture.
Spinal fusion or fixation surgery is one way to treat back pain. Further, spinal fusion or fixation may be used to correct an abnormal curvature of the spine or stabilize the spine due to injury or disease affecting one or more disks or vertebrae. In a spinal fusion procedure, two or more adjacent vertebrae in the spine are fused together. The fusion is typically accomplished by the utilization of spinal instrumentation including pedicle screws and associated rods or plates used to mechanically fix the vertebrae together. Pedicle screws are typically used in spinal fusion surgery because the pedicle serves as a strong mechanical attachment point to the spine. Bone graft material may be utilized to aid in the creation of bone structure between the fused vertebrae to create a single bone.
Spinal fixation components vary depending on the system being utilized but typically include pedicle screws that are inserted through the pedicle and into the vertebral body. The pedicle screws are attached to one another by a linking device, such as a rod or plate, that extends vertically along the row of pedicle screws that are inserted. Several coupling systems are known in the art that are used for coupling the pedicle screws to the linking device, which is oriented parallel to the spinal column. Typically two columns of pedicle screws and linking devices are used, one on each side of the spinal column. After installation, the two linking devices may be attached to one another to provide additional stabilization of that portion of the spine. As an alternative or in addition to pedicle screws, spinal hooks may be used, each spinal hook being coupled to a vertebra via a portion of the vertebral arch.
Because of anatomical variations, the pedicle screws that are fixed to one another in a spinal fusion procedure may not be in longitudinal alignment with one another. Accordingly, spinal fixation systems, whether utilizing a rod or a plate, strive to allow some variability in the placement of the pedicle screws while still accomplishing the goal of fixation with a single rod or plate along the pedicle screws.
One challenge associated with the design of a spinal fixation system is the connection between the pedicle screws and the linking device. Ideally, the number of components involved should be minimized, especially the number of components that must be threaded together (such as nuts and rods) in order to ease the assembly process and minimize the overall time of the surgical procedure.
There is also a need for a spinal fixation system that may be utilized with a minimally invasive surgical approach, such as one that utilizes smaller access apertures or ports rather than a large incision along the entire portion of the spine being treated. A spinal fixation system that addresses the needs for a minimally invasive approach may also address the desire to utilize bone graft material along the fixation site to enhance bony in-growth.
Further, there is a need for a spinal fixation system that not only utilizes fewer components but that requires fewer steps for assembly onto the spine, thus shortening the overall time of the surgical procedure.
It would be desirable to provide a system and/or method that provides one or more of these or other advantageous features or addresses one or more of the above-identified needs. Other features and advantages will be made apparent from the present specification. The teachings disclosed extend to those embodiments that fall within the scope of the appended claims, regardless of whether they accomplish one or more of the above-identified needs.